Method of using sophorolipids in well treatment operations

ABSTRACT

Recovery of fluids from a subterranean formation during a well treatment operation is enhanced by injecting into the formation a treatment fluid comprising a sophorolipid.

This application is a continuation application of U.S. patentapplication Ser. No. 14/685,150, filed on Apr. 13, 2015 which claims thebenefit of U.S. patent application Ser. No. 61/982,198, filed on Apr.21, 2014.

SPECIFICATION Field of the Invention

The invention relates to a method of enhancing the recovery of fluidsfrom a subterranean formation during a well treatment operation byinjecting into the formation a treatment fluid comprising asophorolipid.

Background of the Invention

Hydrocarbons are obtained from subterranean formations by drillingthrough a well that penetrates the formation. This provides a partialflow-path for the hydrocarbons to reach the surface. In order for thehydrocarbons to be produced, there must be a sufficiently unimpededflowpath from the formation to the wellbore to be pumped to the surface.Some wells need to be stimulated due to insufficient porosity orpermeability of the formation. Common stimulation techniques includehydraulic fracturing and acidizing operations. The efficiency inhydrocarbon recovery from such stimulation techniques is dependent onthe development of sufficient channels for the flow of hydrocarbons fromlow permeability regions of the formation.

During hydraulic fracturing, a fracturing fluid, typically a gelled orthickened aqueous solution containing proppant is injected into thewellbore under high pressure and injection rates. Once natural reservoirpressures are exceeded, the fluid induces a fracture in the formationand transports the proppant into the fracture. The fracture generallycontinues to grow during pumping and the proppant remains in thefracture in the form of a permeable pack that serves to “prop” thefracture open. The fractures radiate outwardly from the wellbore andextend the surface area from which oil or gas drains into the well. Theproppant pack forms a highly conductive pathway for hydrocarbons and/orother formation fluids to flow into the wellbore.

An efficient fracturing fluid should possess good proppant transportcharacteristics. Such characteristics are dependent on the viscosity ofthe fluid. Generally, the viscosity should be high in order to achievewider and larger fractures. High viscosity is further generallydesirable for more efficient transport of proppant into the fracturedformation. The fracturing fluid therefore typically contains aviscosifying agent, such as a viscoelastic surfactant or a polymer. Thepolymer may be linear or crosslinked. In certain formations, aqueousacid solutions can be used to improve the permeability of the formation,thereby increasing hydrocarbon production. These acids are oftencombined with polymeric gels to provide an acid fracturing fluid.

A wide range of additives may be used to enhance the rheologicalproperties and/or the chemical properties of the fluid. Such additivesinclude viscosifiers, friction reducing agents, surface active agentsand fluid loss control additives.

After the fracturing fluid is injected into the formation and fractureshave been established, production of hydrocarbons is enhanced throughthe new fractures by removal of the viscous fluid. Generally, theviscosity of the fluid may be decreased by introducing breakers into theformation which degrade the polymer or break the emulsion. However,breakers often result in incomplete breaking of the fluid and/orpremature breaking of the fluid before the fracturing process iscomplete.

Similar to stimulation fluids, other fluids used to treat wells must beremoved following the completion of the treatment operation for whichsuch fluids are used. For instance, polymeric viscosifying agentsfrequently used in drilling muds and well completion fluids have adamaging effect since they tend to interfere with other phases ofdrilling and/or completion operations, as well as production of the wellafter such operations are finished. For example, drilling fluids tend toseep into the surrounding formation forming a filter cake on the wall ofthe wellbore. The filter cake sometimes can prevent casing cement fromproperly bonding to the wall of the wellbore. It is important in suchoperations that the viscosifying agents and other components of thedrilling mud be removed from the well in order to enhance the recoveryof hydrocarbons. Oxidative breakers and enzymes are often used todegrade the polysaccharide-containing filter cakes and residual damagingmaterials which reduce their viscosity.

As an alternative to the use of breakers, or for use in conjunction withbreakers, flowback additives are often introduced into the well toassist in the removal of well treatment fluids. Flowback additives aretypically surfactants. Such surfactants reduce the surface tensionbetween the treatment fluid and hydrocarbons. For instance, in therecovery of hydrocarbon gases, flowback additives enable the recovery ofmore fluid which restores the formation's relative permeability to gas.In addition to fracturing and acidizing operations, there is a need forsuch flowback additives for use in other treatment operations, such assand control operations.

While conventional surfactants have been widely used as flowbackadditives for the removal of treatment fluids from the formation andwell, such surfactants are not environmentally friendly. The need existsfor alternative flowback additives which are biodegradable, non-toxic,and biocompatible and which are based on renewable resources.

SUMMARY OF THE INVENTION

The invention relates to a method of enhancing the recovery of fluidsfrom a subterranean formation during a well treatment operation byinjecting into the formation a treatment fluid comprising asophorolipid.

In an embodiment, the sophorolipid may be a mixture of sophorolipidiccompounds of the formulas (I) and (II):

wherein R¹ is hydrogen or an acetyl group; and either (i) R² is hydrogenor a C₁-C₉ saturated or unsaturated aliphatic group; and R³ is a C₇-C₁₆saturated or unsaturated aliphatic group;

or (ii) R² is hydrogen or a methyl group and R³ is a saturated orunsaturated hydrocarbon chain that contains from 12 to 18 carbon atoms.

In one embodiment, the sophorolipid is a mixture of sophorolipidiccompounds of the formulas (I) and (II) wherein R² is hydrogen or methyl.

In another embodiment, the sophorolipid is a mixture of sophorolipidiccompounds of the formulas (I) and (II) wherein R² is either hydrogen ormethyl and R³ is an unsaturated hydrocarbon chain that contains from 12to 18 carbon atoms.

In an embodiment, the sophorolipids may be a mixture of acidic-formsophorolipids of formula (Ia), where the sophorolipids may be in thefree acid form (—R³—COOH); or acidic-form sophorolipids of formula (Ib),where the acidic-form sophorolipids may be in the neutralized form, as asalt or as a sophorolipid anion (as illustrated in formula (Ib) below)and associated cations (i.e. NH₄ ⁺, Na⁺, K⁺, Ca²⁺, Mn²⁺, or Fe³⁺,(typically Na⁺ or K⁺) that are distributed in the sophorolipidcontaining composition and n is 1, 2, or 3.

-   -   and ester-form sophorolipids of formulas either (IIa) or (IIb),        or mixtures of (IIa) and (IIb), where these ester-form        sophorolipids may be in the closed-ring form that may also be        referred to as lactonic sophorolipids, or where the        sophorolipids are in the open-ring form but the carboxyl acid        moiety is esterified with, for example, a suitable alcohol or        other hydroxyl-containing compound (—R³—COOR⁴, as an ester),

wherein R¹ is hydrogen, a C₁ to C₄ hydrocarbon or carboxylic acid group(typically an acetyl group); and either (i) R² is hydrogen or a C₁-C₉saturated or unsaturated aliphatic group; and R³ is a C₇-C₂₀ saturatedor unsaturated aliphatic group; or (ii) R² is hydrogen or a methyl groupand R³ is a saturated or unsaturated hydrocarbon chain that containsfrom 7 to 20 carbon atoms. Typically R² is a hydrogen or methyl or ethylgroup, (preferably a methyl group or hydrogen). Typically R³ is C₇ toC₂₀ saturated or unsaturated aliphatic group a C₇ to C₂₀ (preferred isC₁₅ monounsaturated), and R⁴ is hydrogen, C₁-C₉ saturated or unsaturatedaliphatic group, monohydroxyl aliphatic group, or polyhydroxyl aliphaticgroup (preferred is hydrogen group).

In one embodiment, the sophorolipid is a mixture of sophorolipidcompounds of the formulas (Ia) and (IIa) wherein R² is hydrogen or a C₁to C₄ hydrocarbon (typically methyl).

In another embodiment, the sophorolipid is a mixture of acidic-formsophorolipids where at least portion of the acid moiety is neutralizedwith a base to form a salt or where the sophorolipid anion andassociated cations of formula (lb), as described above, are distributedin the sophorolipid containing composition, and ester-form sophorolipidsas described in formulas (IIa) and (IIb). In yet another embodiment, allor any combination of the forms of the above describe sophorolipids maybe in the composition.

In an embodiment, the sophorolipid used in the well treatment fluid isgreater than 90% pure.

In another embodiment, the sophorolipid used in the well treatment fluidis greater than 95% pure.

In an embodiment, the treatment fluid containing the sophorolipid isused in a hydraulic fracturing well treatment operation.

In another embodiment, the treatment fluid containing the sophorolipidis used in a drilling operation.

In another embodiment, the treatment fluid containing the sophorolipidis used in a sand control operation.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more fully understand the drawings referred to in thedetailed description of the present invention, a brief description ofeach drawing is presented, in which:

FIG. 1 illustrates the compatibility of a sophorolipids in guar basedwell treatment fluids.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A sophorolipid may be incorporated into a well treatment fluid. Thesophorolipid is particularly useful as a flowback additive to enhancethe recovery of fluids used in well treatment operations.

Sophorolipids may be manufactured from corn (or other grain-based media)and vegetable oil with variations in the process being dependent on thenatural and non-pathogenic yeast strand and production medium. As such,sophorolipids are naturally occurring bio-surfactant glycolipidsproduced from yeasts. For instance, the sophorolipids are glycolipidsproduced fermentatively from such yeasts as Candida bombicola, Candidaapicola, and Wickerhamiella domercqiae. Sophorolipids are generallycomposed of a dimeric sophorose sugar moiety (β-D-Glc-(1→2)-D-Glc)linked glycosidically to a hydroxyl fatty acid residue. In a preferredembodiment, a sophorose sugar moiety is linked via the glycosidiclinkage to the hydroxyl group of a 17-hydroxy-C₁₈ saturated or monoenoic(cis-9) fatty acid.

Depending on the pH of the system, sophorolipids can assume a circular,lactonic sophorolipid form or a linear, acidic sophorolipid form.Usually the 6-hydroxyl groups of the glucose moieties are acetylated.Depending upon the organism and the fermentation conditions used toproduce the sophorolipid, the acidic or lactone form may predominate.

Suitable sophorolipids for use in the disclosure are those set forth inU.S. patent application Ser. No. 61/981,951, filed on Apr. 21, 2014 andU.S. patent application Ser. No. 61/981,964, filed on Apr. 21, 2014,both of which are herein incorporated by reference in their entirety.

In a preferred embodiment, the sophorolipid is a mixture ofsophorolipidic compounds represented by the formulas (I) and (II):

wherein R¹ is hydrogen or an acetyl group; and either R² is hydrogen ora C₁-C₉ saturated or unsaturated aliphatic group; and R³ is a C₇-C₁₆saturated or unsaturated aliphatic group; or R² is hydrogen or methyland R³ is a saturated or unsaturated hydrocarbon chain that containsfrom 12 to 18 carbon atoms, more preferably from about 13 to about 17carbon atoms.

As illustrated, the hydroxyl fatty acid moiety of the acidicsophorolipids may remain a free acid (I) or form a macrocyclic lactonering with the 4″-OH group of the sophorose lactone form (II). Suchsophorolipidic compounds may be prepared by conventional methods knownin the art, such as those disclosed in U.S. Pat. No. 5,879,913, hereinincorporated by reference.

In an embodiment, the sophorolipid is a mixture of sophorolipidiccompounds of the formulas (III) and (IV):

As described above, the sophorolipids may be a mixture of acidic-formsophorolipids of formula (Ia), where the sophorolipids may be in thefree acid form (—R³—COOH); or acidic-form sophorolipids of formula (Ib),where the acidic-form sophorolipids may be in the neutralized form, as asalt or as a sophorolipid anion (as illustrated in formula (Ib) below)and associated cations (i.e. NH₄ ⁺, Na⁺, K⁺ Ca²⁺, Mn²⁺, or Fe³⁺,typically Na⁺ or K⁺) that are distributed in the sophorolipid containingcomposition and n is 1, 2, or 3.

-   -   and ester-form sophorolipids of formulas either (IIa) or (IIb),        or mixtures of (IIa) and (IIb), where these ester-form        sophorolipids may be in the closed-ring form that may also be        referred to as ester sophorolipids, or where the sophorolipids        are in the open-ring form but the carboxyl acid moiety is        esterified with, for example, a suitable alcohol or other        hydroxyl-containing compound (—R³—COOR⁴, as an ester),

wherein R¹ is hydrogen, a C₁ to C₄ hydrocarbon or carboxylic acid group(typically an acetyl group); and either (i) R² is hydrogen or a C₁-C₉saturated or unsaturated aliphatic group; and R³ is a C₇-C₂₀ saturatedor unsaturated aliphatic group; or (ii) R² is hydrogen or a methyl groupand R³ is a saturated or unsaturated hydrocarbon chain that containsfrom 7 to 20 carbon atoms. Typically R² is a hydrogen or methyl or ethylgroup, (preferably a methyl group or hydrogen). Typically R³ is C₇ toC₂₀ saturated or unsaturated aliphatic group a C₇ to C₂₀ (preferred isC₁₅ monounsaturated), and R⁴ is hydrogen, C₁-C₉ saturated or unsaturatedaliphatic group, monohydroxyl aliphatic group, or polyhydroxyl aliphaticgroup (preferred is hydrogen group). In one embodiment, the sophorolipidis a mixture of sophorolipids compounds of the formulas (Ia), (Ib),(IIa), and/or (IIb) wherein R² is hydrogen or methyl.

In another embodiment, the sophorolipid is a mixture of acidic-formsophorolipids where the acid moiety is at least partially neutralizedwith a base to form a salt or anion and cation distributed in thesophorolipid containing composition as described above, and ester-formsophorolipids where the carboxylic moiety is a lactone or an open chainester-form sophorolipid (i.e. where the lactone ring is in open form butthe acid moiety is esterified with a suitable hydroxyl containingcompound such as, for example, glycerol or some other hydroxylcontaining compound, such as mono- and poly-alcohols), or mixturesthereof. In yet another embodiment, all or any combination of the abovedescribe sophorolipids may be in the composition.

Typically, the pH of the well treatment fluid containing thesophorolipid is from about 7.0 to about 13.0, more typically from about8.5 to about 10.5.

The dry solids of materials made from such processes is typicallygreater than about 90%, more typically greater than about 95%,sophorolipid. Typically, there are some free fatty acids (preferably nogreater than 5%) and a small amount of vegetable oil in the reactionproduct.

The sophorolipids described herein have particular applicability asflowback additives in a well treatment operation. As flowback additives,the sophorolipids function as biosurfactants in reducing the surfacetension between the treatment fluid containing the sophorolipid and theproduced hydrocarbons. This enables the recovery of more fluid from theformation and enhances or restores the formation's relative permeabilityto hydrocarbons.

In addition to being biodegradable, the sophorolipid biosurfactants arenon-toxic, biocompatible and are made from renewable resources. The useof sophorolipid biosurfactants in well treatment fluids provides a greenalternative to treatment fluids containing conventional flowbacksurfactants. In well treatment operations, such as hydraulic fracturing,which present environmental concerns, sophorolipid biosurfactantsprovide an attractive alternative to conventional synthetic surfactants.They further maximize the benefits of a fracturing operation byimproving the recovery of the treatment fluid introduced into theformation.

The treatment fluid containing the sophorolipid may be fresh water, saltwater, brine or may further be non-aqueous, such as methanol, ethyleneglycol, etc. The fluid may further be a foamed fluid especially where itis desired to be used for deeper proppant penetration or in watersensitive zones.

While the sophorolipid may be a component of a well treatment fluid andpumped into the wellbore during a well treatment operation, a fluidcontaining the sophorolipid may also be pumped into the wellbore priorto or subsequent of such treatment operation. For example, during a welltreatment operation (such as a drilling, stimulation or gravel packingoperation), a fluid which is later desired to be recovered (a“recoverable fluid”) may be pumped into the wellbore. This fluid may be,for instance, a fracturing fluid, a matrix stimulation fluid, anacidizing fluid, a hydrocarbon-based treatment fluid, a drilling mud, adrill-in fluid, a workover fluid, a packer fluid or a completion fluid.The sophorolipid may be a component of the recoverable fluid.

Alternatively, a precursor fluid may be pumped into the wellbore priorto the recoverable fluid. This precursor fluid may contain thesophorolipid. As an example, a spearhead fluid containing thesophorolipid may be pumped into the wellbore prior to the pumping of thefracturing fluid.

In another alternative, a post fluid may be pumped into the wellboresubsequent to the pumping of the recoverable fluid. This post fluid maycontain the sophorolipid. As an example, a diverter fluid may be pumpedinto the wellbore subsequent to the pumping of the fracturing fluid. Thediverter fluid may contain the sophorolipid.

In an embodiment, the sophorolipid may be a component of a fluidcontaining a viscosifying agent. The viscosifying agent may be asynthetic or natural polymer as well as a viscoelastic surfactant.

The synthetic or natural polymer may contain one or more functionalgroups, such as a hydroxyl, carboxyl, sulfate, sulfonate, amino or amidogroup. Preferred synthetic and natural polymers include polysaccharidesand derivatives thereof, polyvinyl alcohols, polyacrylates (includingthe (meth)acrylates), polypyrrolidones, polyacrylamides (including(meth)acrylamides) as well as 2-acrylamido-2-methylpropane sulfonate andmixtures thereof.

Suitable polysaccharides and derivatives include those which contain oneor more monosaccharide units of galactose, fructose, mannose, glucoside,glucose, xylose, arabinose, glucuronic acid and pyranosyl sulfate. Theseinclude non-derivatized and derivatized guar gums, locust bean gum,tara, xanthan, succinoglycan, scleroglucan and carrageenan. Thesepolysaccharides include guar gums and derivatives, starches andgalactomannan gums. In a preferred embodiment, guar gum may beunderivatized guar or a derivatized guar, such as a hydroxyalkyl guar(like hydroxypropyl guar), a carboxyalkyl guar (like carboxymethyl guar)and a carboxyalkylhydroxyalkyl guar like carboxymethylhydroxypropyl).

Further, the polysaccharide may be a cellulose or cellulose derivativesuch as an alkylcellulose, hydroxyalkyl cellulose or alkylhydroxyalkylcellulose, carboxyalkyl cellulose derivatives such as methyl cellulose,hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxybutyl cellulose,hydroxyethylmethyl cellulose, hydroxypropylmethyl cellulose,hydroxybutylmethyl cellulose, methylhydroxyethyl cellulose,methylhydroxypropyl cellulose, ethylhydroxyethyl cellulose,carboxyethylcellulose, carboxymethylcellulose andcarboxymethylhydroxyethyl cellulose.

When the viscosifying agent is polymeric, the fluid may further containa crosslinking agent. Suitable crosslinking agents include borate ionreleasing compounds, organometallic or organic complexed metal ionscomprising at least one transition metal or alkaline earth metal ion aswell as mixtures thereof.

Borate ion releasing compounds which can be employed include, forexample, any boron compound which will supply borate ions in the fluidupon disassociation from the deformable core. Such compounds includeboric acid, alkali metal borates such as sodium diborate, potassiumtetraborate, sodium tetraborate (borax), pentaborates and the like andalkaline and zinc metal borates. Such borate ion releasing compounds aredisclosed in U.S. Pat. Nos. 3,058,909 and 3,974,077 herein incorporatedby reference. In addition, such borate ion releasing compounds includeboric oxide (such as selected from H₃BO₃ and B₂O₃) and polymeric boratecompounds. Mixtures of any of the referenced borate ion releasingcompounds may further be employed. Such borate-releasers typicallyrequire a basic pH (e.g., 8.0 to 12) for crosslinking to occur.

Further preferred crosslinking agents are those, such as organometallicand organic complexed metal compounds, which can supply trivalent orhigher polyvalent metal ions into the fluid upon their disassociationfrom the deformable core. Examples of the trivalent or higher polyvalentmetal ions include boron, titanium, zirconium, aluminum, yttrium,cerium, etc. or a mixture thereof. Examples of titanium compoundsinclude titanium ammonium lactate, titanium triethanolamine, titaniumacetylacetonate, titanium diisopropoxide bisacetyl aminate, titaniumtetra(2-ethyl hexoxide), titanium tetraisopropoxide, titaniumdi(n-butoxy) bistriethanol aminate, titanium isopropoxyoctyleneglycolate, titanium diisopropoxy bistriethanol aminate and titaniumchloride. Examples of zirconium salts include zirconium ammoniumcarbonate, zirconium carbonate, zirconium acetylacetonate, zirconiumdiisopropylamine lactate, zirconium chloride, zirconium lactate,zirconium lactate triethanolamine, zirconium oxyacetate, zirconiumacetate, zirconium oxynitrate, zirconium sulfate, tetrabutoxyzirconium(butyl zirconate), zirconium mono(acetylacetonate), zirconium n-butyrateand zirconium n-propylate. The crosslinking agent may optionally beencapsulated. Examples of typical crosslinking agents include, but arenot limited to, those described in U.S. Pat. Nos. 4,514,309 and5,247,995, which are incorporated herein by reference.

Further, the viscoelastic surfactant may be any viscoelastic surfactantknown in the art. Preferred are those viscoelastic surfactantscontaining an anionic surfactant and a cationic surfactant. A mostpreferred viscoelastic surfactant is the combination of sodium xylenesulfonate, as anionic surfactant, and N,N,N-trimethyl-1-octadecammoniumchloride, as cationic surfactant. Such viscoelastic surfactants are setforth in U.S. Pat. No. 6,468,945, herein incorporated by reference. Thevolume ratio of anionic surfactant:cationic surfactant is from about 1:4to about 4:1.

Other preferred viscoelastic surfactants are those which contain a C₁₀to C₂₄ alkyl trialkyl quaternary ammonium aromatic salt admixed with ananionic surfactant, such as sodium xylene sulfonate. Such systemsinclude those set forth in U.S. Patent Publication No. 20040138071,herein incorporated by reference. Typically, the volume ratio ofcationic surfactant:anionic surfactant of such viscoelastic surfactantsis between from about 1:1 to about 3:1. The alkyl group forming thealkylated moiety can be a C₁₀ to C₂₄ alkyl group, preferably a C₁₂ to aC₂₀ alkyl. In a most preferred embodiment, the alkyl group forming thealkylated moiety is a C₁₈ alkyl. The aromatic salt is preferably anaromatic salicylate or phthalate. The trialkyl moiety containspreferably from C₁ to C₄ alkyl groups, most preferably methyl. In apreferred mode, the surfactant is a gelled C₁₈ trimethyl quaternaryammonium phthalate or a gelled C₁₈ trimethyl quaternary ammoniumsalicylate. Such C₁₀ to C₂₄ alkyl trialkyl quaternary ammonium aromaticsalts may be formed by mixing a C₁₀ to C₂₄, preferably a C₁₈, alkyltrialkyl quaternary ammonium chloride with an alkali aromatic salt, suchas a sodium salt of either salicylic acid or phthalic acid.

The fluid containing the sophorolipid may further contain a breaker fordefragmenting the viscosifying polymer and reducing the viscosity of thetreatment fluid. Suitable are enzymatic and oxidative delayed breakers.Examples of suitable materials include, but are not limited to, amines,acids, acid salts, acid-producing materials, etc. The breaker ispreferably an acid breaker such as hydrochloric acid, formic acid orsulfamic acid or alternatively a basic breaker such as sodium bisulfate.The oxidizing agent is preferably an alkaline earth peroxide, anencapsulated persulfate, a catalyzed organic peroxide or a hydrochloritebleach.

In a preferred embodiment, the sophorolipid is used as flowback additivein a drilling fluid to enhance the recovery of the fluid havingsuspended solids and cuttings out of the wellbore. Such fluids, inaddition to the viscosifying agent, typically may contain weightingagents.

In another preferred embodiment, the sophorolipid is used as a flowbackadditive in a hydraulic fracturing or a sand control operation.

In a preferred embodiment, the sophorolipids may be used in slickwaterfracturing, a type of hydraulic fracturing that uses a low viscosityaqueous fluid to induce the subterranean fracture. The fluid containingthe sophorolipid for use in slickwater fracturing typically has aviscosity only slightly higher than unadulterated fresh water or brineand typically contains a friction reduction agent. The fluid may furthercontain a non-crosslinked or linear gel. Typically, the frictionreduction agent present in slickwater does not increase the viscosity ofthe fracturing fluid by more than 1 to 2 centipoises (cP). Theslickwater fluid may be crosslinked or may consist of a linearviscosifying agent.

The sand control method may use the well treatment fluid in accordancewith any method in which a pack of particulate material is formed withina wellbore that it is permeable to fluids produced from a wellbore, suchas oil, gas, or water, but that substantially prevents or reducesproduction of formation materials, such as formation sand, from theformation into the wellbore. Such methods may or may not employ a gravelpack screen, may be introduced into a wellbore at pressures below, at orabove the fracturing pressure of the formation, such as frac pack,and/or may be employed in conjunction with resins such as sandconsolidation resins is so desired.

A fracturing fluid containing a sophorolipid may further contain aproppant. Such proppants include conventional proppants such as sand,glass beads, walnut hulls, and metal shot as well as resin-coated sands,intermediate strength ceramics, and sintered bauxite as well ultralightweight proppants (ULW) having an apparent specific gravity lessthan or equal to 2.45. Such proppant include those disclosed in U.S.Pat. Nos. 6,364,018, 6,330,916; 6,059,034; 7,426,961; 7,322,411;7,528,096; and 7,931,087, herein incorporated by reference.

The fluid may further contain one or more well treatment agents such ascorrosion inhibitors, surfactants, biocides, surface tension reductionagents, friction reducers, scale inhibitors, clay stabilizers and ironcontrol agents.

The sophorolipid may be combined with the other components of the fluidin a batch process performed at the wellsite using mixing vessels or maybe batched mixed away from the wellsite and transported to the wellsite.In a preferred embodiment, the fluid containing the sophorolipid isprepared on the fly using continuous mixing methods at the wellsite.

The following examples are illustrative of some of the embodiments ofthe present invention. Other embodiments within the scope of the claimsherein will be apparent to one skilled in the art from consideration ofthe description set forth herein. It is intended that the specification,together with the examples, be considered exemplary only, with the scopeand spirit of the invention being indicated by the claims which follow.

All percentages set forth in the Examples are given in terms of weightunits except as may otherwise be indicated.

EXAMPLES Example 1

Fluid recovery was used to check the initial response of a sophorolipidbiosurfactant by packing a column with 20/40 Ottawa sand. Nitrogen gaspressure was used to simulate production and flowed at a controlled rateto recover the fluid from the column. A flow meter was calibrated to getthe desired flow rate of the fluid to be 8 cc/sec at 20 psi. Thebiosurfactant was tested at 1 gallon per one thousand gallons of tapwater (gpt) and 2% KCl. The biosurfactant was also tested at 0.5 gpt intap water at a pH of 5.0 and 11.0. The recovered amount of fluid fromthe column was captured and divided by the initial, known volume and apercent recovered volume calculated. Base fluid recovery withoutaddition of surfactants gave fluid recovery below 60%. The results areset forth in Table I wherein Biosurfactant A is a sophorolipidcomprising a mixture of formulas (III) and (IV). Biosurfactant B is a50:50 v/v mixture of Biosurfactant A and ethylene glycol (as winterizingagent).

TABLE I Base Fluid- Base fluid- 1 gpt, 0.5 gpt, 0.5 gpt, water 0.5 gpt,water, Tap water 2% KCl Product 1 gpt, water 2% KCl water pH of 5.0 pHof 11.0 54.2% 54.6% A 87.0% 84.4% 85.9% 86.0% 89.0% B 87.1% 77.6% 87.8%84.4% 89.5%Table 1 demonstrates that as little as 0.5 gpt of a 1% solution ofBiosurfactant A and Biosurfactant B produces a favorable recovery ofbase fluid.

Fluid recovery was then tested on two non-lipid synthetic fluid lossrecovery additives, commercially available from Baker HughesIncorporated. The results are shown in Table II and illustrate that thebiosophorolipid additives exhibit the approximate percent fluid lossrecovery as non-lipid additives.

TABLE II Product 1 gpt, water 1 gpt, 2% KCl C 88.5% 87.0% D 88.6% 86.3%

Example 2

Into 1 l of water was added, with vigorous stirring, 6.25 gpt of anunderivatized guar having an intrinsic viscosity of about 16.3 dl/g, 1.5gpt of a borate crosslinker, commercially available as XLW-30 from BakerHughes Incorporated, and 1.5 gpt of a potassium containing buffercapable of adjusting the pH of the fluid to a range of about 11.0,commercially available as BF-9L from Baker Hughes Incorporated. Aftergelation, the compatibility of two sophorolipids containing compounds offormulas (III) and (IV) with a 25 ppt of the guar based fluid wasrheologically tested on a Fann 50 viscometer. The crosslinked fluid wastested at a constant shear rate of 100 sec⁻¹ with a shear rate ramp of100, 80, 60, 40 sec⁻¹ at 75° F. initially and then every 30 minutes at200° F. for 3 hours. The Fann 50 bath was pre-heated to a 200° F. Theresults, set forth in FIG. 1, demonstrate the compatibility of thebiosurfactants with the guar based fluid.

From the foregoing, it will be observed that numerous variations andmodifications may be effected without departing from the true spirit andscope of the novel concepts of the invention.

What is claimed is:
 1. A method of enhancing recovery of a welltreatment fluid from a well comprising: (a) introducing into the wellthe well treatment fluid, the well treatment fluid comprising at leastone sophorolipidic compound selected from the group consisting of:

(b) treating the well with the well treatment fluid during a welltreatment operation; and (c) recovering the well treatment fluidcontaining the sophorolipidic compound from the well after step (b),wherein the recovery of the well treatment fluid is enhanced by thesophorolipidic compound in the well treatment fluid.
 2. The method ofclaim 1, wherein (I) and (II) are in equilibrium with each other.
 3. Themethod of claim 1, wherein the well treatment operation is a hydraulicfracturing operation and further wherein the well treatment fluid is afracturing fluid and is introduced into the well during the hydraulicfracturing operation, the fracturing fluid inducing a fracture in asubterranean formation penetrated by the well.
 4. The method of claim 1,wherein the well treatment operation is slickwater fracturing andfurther wherein the well treatment fluid is a fracturing fluidintroduced into the well during slickwater fracturing, the fracturingfluid inducing a fracture in a subterranean formation penetrated by thewell.
 5. The method of claim 1, wherein the well treatment operation isa drilling operation and further wherein the well treatment fluid is adrilling mud, the drilling mud being introduced into the well during thedrilling operation.
 6. The method of claim 1, wherein the well treatmentoperation is a gravel packing operation and further wherein the welltreatment fluid is introduced into the well during the gravel packingoperation.
 7. The method of claim 1, wherein the well treatmentoperation is an acidizing operation and further wherein the welltreatment fluid is an acidizing fluid, the acidizing fluid beingintroduced into the well during the acidizing operation.
 8. The methodof claim 1, further comprising producing hydrocarbons from asubterranean formation penetrated by the well wherein surface tensionbetween the well treatment fluid and the produced hydrocarbons isreduced by the sophorolipidic compound in the well treatment fluid. 9.The method of claim 8, further comprising enhancing the permeability ofthe subterranean formation to the produced hydrocarbons by thesophorolipidic compound in the well treatment fluid.
 10. The method ofclaim 1, wherein the well treatment fluid comprising the sophorolipidiccompound is a matrix stimulation fluid.
 11. The method of claim 1,wherein the well treatment fluid comprising the sophorolipidic compoundis a drill-in fluid, a workover fluid, or a packer fluid.
 12. The methodof claim 1, wherein the well treatment fluid is a completion fluid. 13.The method of claim 1, wherein the well treatment operation is adiversion treatment conducted after a subterranean formation penetratedby the well is fractured and further wherein the well treatment fluidcomprising the sophorolipidic compound is a diverter fluid.
 14. Themethod of claim 1, wherein the fluid further comprises underivatized orderivatized guar.
 15. The method of claim 14, wherein the fluid furthercomprises a crosslinking agent.
 16. A method of increasing recovery of awell treatment fluid injected into a well during a drilling, stimulatingor gravel packing operation, the method comprising introducing into awell during the drilling, stimulating or gravel packing operation thewell treatment fluid, the well treatment fluid comprising at least onesophorolipidic compound selected from the group consisting of:

wherein the amount of the well treatment fluid recovered from the wellafter the drilling, stimulating or gravel packing operation is enhancedby the presence of the sophorolipidic compound in the well treatmentfluid injected into the well.
 17. The method of claim 16, wherein thewell treatment fluid comprises guar and a crosslinking agent.
 18. Themethod of claim 17, wherein the guar is underivatized or derivatizedguar.
 19. A method of fracturing a subterranean formation penetrated bya wellbore, the method comprising: (a) pumping a fracturing fluid intothe wellbore at a pressure sufficient to create or enlarge a fracture;(b) producing fluid from the created or enlarged fracture; and whereinthe method further comprises either: (i) pumping a spearhead fluid intothe wellbore prior to step (a), the spearhead fluid comprising at leastone sophorolipidic compound; or (ii) pumping a diverter fluid into thewellbore after step (b), the diverter fluid comprising at least onesophorolipidic compound and wherein the sophorolipidic compound isselected from the group consisting of:


20. The method of claim 19, wherein (I) and (II) are in equilibrium witheach other.